Project Outputs

Shatto Ditch Watershed

Impact of cover crops on tile and stream water quality in Shatto Ditch Watershed

Since cover crop coverage has been expanded to >65% of the watershed, our water samples from tile drains have shown a marked decrease in nutrient export from fields to the stream. Our results are proving that planting cover crops over winter retains nutrients for the following spring's cash crop; nutrients that would otherwise have been washed out of the fields at a loss to the farmer and to the detriment of the water environment.

​We combined water chemistry and stream discharge data from 2012-2014 to estimate total annual nitrogen (N) and phosphorus (P) export from the watershed before and after cover crops. We found significant reductions in both N and P export at the watershed scale, translating to ~30-40% reduction in NO3-N and SRP export from the watershed annually. We continue to collect data and expect to be able to report a continuing trend. ​You can download summaries of our results so far here:

Watch this short interview with Dr. Tank about the results we've been getting.

Impact of cover crops on soil health in both watersheds

Our soil sampling in both watersheds has consistently showed that soil nitrate (NO3-N) at 0-20cm deep is lower in cover crop fields when cover crops are actively growing compared to those fields without cover crops. This indicates that N is tied up in cover crop tissue during it's growing time in fall and spring which suggests that this NO3 will then become available for the summer cash crop.

​We have found no significant difference in Water-Extractable Phosphorus (WEP) in cover crop fields compared to bare fields.. We have not yet observed a significant increase in soil organic matter in fields with cover crops in Shatto Ditch Watershed compared to those without. However, we have seen an increase in soil organic matter in fields with cover crops in the Kirkpatrick Ditch Watershed.

Impact of cover crops on tile and stream water quality in Kirkpatrick Ditch Watershed

Cover crops were planted on 23% of the watershed in Fall 2015 and our 'before and after' data is showing similar positive trends to our Shatto Ditch results. NO3 from tile drains with cover crops declined, particularly in spring, and stream NO3 concentration was also lower in the first year after cover crop planting. Our data do not show cover crops increasing loss of dissolved phosphorus from tile drains. We continue to monitor and are analyzing data from the 2017 water year (after 24% of the watershed was planted with cover crops in Fall 2016).